How to get current position of an object using Blender's Python API in BGE?
When are you reading the value?  If you've assigned it to a variable, it might be reading the initial value, and ignoring any updates.  

You'll need to update the value periodically.  Possibly using an Always sensor, with a skip, if desired.  Or at certain times within the game;  collision with another object, for instance.  

You may need to access appropriate coordinate within it's location vector:  obj.pos.x